%0 Generic
%A Fukazawa, Aiko
%A Oshima, Hiroya
%A Shimizu, Soji
%A Kobayashi, Nagao
%A Yamaguchi, Shigehiro
%D 2014
%T Dearomatization-Induced
Transannular Cyclization:
Synthesis of Electron-Accepting Thiophene‑S,S‑Dioxide-Fused Biphenylene
%U https://acs.figshare.com/articles/dataset/Dearomatization_Induced_Transannular_Cyclization_Synthesis_of_Electron_Accepting_Thiophene_i_S_i_i_S_i_Dioxide_Fused_Biphenylene/2283712
%R 10.1021/ja503499n.s003
%2 https://acs.figshare.com/ndownloader/files/3920173
%K 4π electrocyclic reaction sequence
%K transannular cyclization
%K thiophene
%K oxidation
%K Fc
%K biphenylene
%K dehydroannulene
%K room temperature
%X The transannular cyclization of dehydroannulenes
bearing several
alkyne moieties in close proximity is a powerful synthetic method
for producing polycyclic aromatic hydrocarbons. We report that the
reactivity can be switched by the aromaticity of the ring skeletons
fused with the dehydroannulene core. Thus, while thiophene-fused bisdehydro[12]annulene 1 was handled as a stable compound in the air at room temperature,
the oxidation with m-chloroperbenzoic acid from the
aromatic thiophene rings to the nonaromatic thiophene-S,S-dioxides induced the transannular cyclization,
even at room temperature, which was completed within 1 day to produce
the formal [2 + 2] cycloadduct 3. This is in stark contrast
to the fact that the thermal cyclization of 1 itself
required heating at 80 °C for 9 days for completion. Experimental
and theoretical studies indicate that the oxidation of even one thiophene
ring in 1 sufficiently decreases the activation barrier
for the transannular cyclization that proceeds through the 8π
and 4π electrocyclic reaction sequence. The thiophene-S,S-dioxide-fused biphenylene 3 thus produced exhibits a set of intriguing properties, such as a
higher electron affinity (E1/2 = −1.17
V vs Fc and Fc+) and a stronger fluorescence (ΦF = 0.20) than the other relevant biphenylene derivatives,
which have electron-donating and nonfluorescent characteristics.
%I ACS Publications